I’ve used an orthostatic (Rusko) test almost daily for a couple years. Although the most conservative and hardest to interpret, I think it’s the method with the least chance of false positives. It’s the least likely to cause overtraining.
Orthostatic test results are highly personalized, but when I’ve had similar results–a heart rate that doesn’t decline after the initial standing spike–it usually means that I need more recovery.
It’s really important to establish a series of baseline results during a recovery week. Did you start using the test during a build week by chance?